Signaling system



Sept. 22,1936. y A, MfURTls 2,054,790

SIGNALING SYSTEM Filed Oct. 28, 1932 RECEIVE 2A/VENTO@ A. M. CURTIS A TTORNEV' Patented Sept. 22, 1936 PATENT oFFloE Y STGNALING SYSTEM Austen M. Curtis, `'East Orange, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application October28, 1932, Serial No. 640,030

4 Claims.

This invention relates to signaling systems and more particularly to such systemswhich include long deep sea telephone and/or telegraph cables.

When an emergency arises at one of the terminals of a long submarine signaling cable which interrupts the regular communication channels, it becomes highly desirable to communicate immediately with the distant end. The system needed for such a purpose mustbe complete in itself, entirely independent of the regular power supply, and ready at all times to transmit and receive signals with only the cable intact as the means for transmission. In addition to being of value as an emergency device such a system will also be of use as a means of communica- -tion between the cable stations at thetime that the regular terminal equipment of thecable is being installed and tested.

`apparatus has ceased to operate. v

Afurther object of the invention is to provide an emergency telegraph system which will be simple to operate and sufficiently reliablefor use on long `deep sea signaling lines;

In pursuance of these objects the present iny vention contemplates thetransmission from the sending station of a submarine cable of low frequency Vsignaling impulses, the spacing impulses being negative and the -marking impulses positive, or lvice versa. In orderto somewhat-preshape these impulses, there is provided a -pre'shaping network Whichcomprises a condenser and a resistance element. At the receivingstation of the cable there is provided a receiving shaping system which comprises a shunted receiving condenser in series with the cable, and an adjustable inductive shunt of variable resistance bridged yaround a detecting circuit. This detecting circuit comprises a pair of head telephones which is connected in series with a transmitter-microphone button, or a tuning fork tone device.

'Ihe low frequency signaling impulses are modulated by the vibrating reed of the microphone button to generate a high frequency component which is rendered audible in the telephone receiver.

The invention will now be described in more detail with reference to the accompanying drawing which schematically illustrates a schematic diagram of the circuits and apparatus employed at each end of the signaling line.

(ci. 17a-69) The drawing shows a submarine signaling cable 8 and a sea earth cable 9. During normal operation of` the signaling system the cable is connected through switch 2l to the regular signaling circuits, indicated at 30. The emergency L'5 telegraph circuit comprises a batterywl with a center tap and an ordinary backand front contact telegraph key II. An additional key or call button I 2 is provided to allow the transmission `of a signal which will give an audible alarm at the `10 vreceiving end of the cable 8. An adjustable send- -ing condenser C is connected between the cable `and the key I I in order to somewhat preshape the transmitted signals. A send-receive switch I3 is arranged so that either the receiving circuitA or 15 the transmitting circuit may be connected tothe cable. Since the received signal consists of groups of low frequency` pulses,r the spacing pulses being. negative and the marking 'pulses positive, or vice versa, a receiving shaping sys- 20 Vtem I4 analogous to that used in ordinary low speed cable telegraphy is preferably used. This consists of shunted receiving condenser Cin se- 'ries with the cable and an adjustableinductive shuntl `with Variable resistances I5 and I5. 25 Polar relay I1 operates on received call signals only;` its windings are connected in series with the receiving condenser shunt but play no ap'- preciable'part in the shaping of the telegraph signals. In practical experiments it has been' found 130 possible to use the same condenser and shuntin both sending and Vreceiving positions without making any changes in the shaping adjustments. The only adjustment necessary in the latter case .isin the potentiometer 24.

The. emergency receiving circuit comprises a pair of; head telephones I9 in series with a transmitter microphone button 20 mountedon a reed 2I which is vibrated by a second button 22 and a telephone receiver element 23 at a frequency of the order of 1000 cycles. As the spacing element of the transmitted signal produces a steadyA voltage, it is necessary to oppose this voltage by means of a potentiometer 24 and a battery 25 in order thatthe spacing position of the ysending key will correspond to silence in the telephone receiver. When Ythe sending key II is depressed, the opposite. voltage is applied to the cable and the signal produced by the entire sending battery voltage, attenuated, of course, by the cable, is available at the terminals of the detector as a low frequency direct current pulse. This pulse is modulated by the microphone button and is heard in the receiver as a tone. The potentiometer and battery compensate merely for the drop of potential produced by the spacing element of the transmitted signal across the in ductive shunt and its associated resistance i5.

The operation of the emergency system is as follows:

In normal operation, the regular receiving apparatus at both terminals are connected to the cable. Also, the polar relay l? whose windings are included in the receiving condenser' shunt, is connected so that the spacing signal normally holds its armature against the spacing contact SC as shown. (As there appear in this part of the circuit only the very low frequencyrcomponents of the signal, the normally transmitted marking signal will not operate this relay.) When an emergency arises at one of the terminal stations which precludes the use of the regular telephone or telegraph channels the operator located at this station actuates switch 2l' which disconnects the cable il from the normal circuit and connects it to theV emergency Vcircuit, and sets his send-receive key in the sending position. He then pushes the call alarm butto-n I2. The call alarm button I2 operates relay 23 which automatically disconnects the shaping networks and places the full transmitting battery on the cable through the protective resistance 29. If the operator at the far 'end-has not become aware of trouble due to a cessation oi trailic, this direct current pulse will cause the vmeters in his receiving circuits to deect violently due to blocking of the receiving amplifiers.

ing of relay I1 is suicient to throw the armature of relay II to its marking contact MC and to ring the alarm bell VI8 which is connected to the marking contact. In order to avoid operation of the calling device at the transmitting end l of the cable when the. same condenser is used as sending and receivingcondenser, additional `contact 39 attached to the send-receive switch may be utilized to short-circuit the windings of the relay When the switchv is turned to the sending position.

It is understoodr that the scope. of the invention is not limited tothe use ofa reed and a microphone button for modulating the incoming low frequency impulses, but that other suitable instrumentalities (a tuning fork tone device, for

He then con-V Vnects his emergency set ,to the cableand an'- instance) may be used as equivalents without thereby departing from the spirit of the present invention.

What is claimed is:

l. A signaling system comprising a deep sea signaling cable, a source of current for transmitting impulses of low frequency over said cable, vibrating means at the receiving end of said cable, and modulating means connected to the receiving end of said cable and to said vibrating means for modulating the low frequency signal impulses to produce a high frequency component, and Vmeans for rendering audible said high frequency component.

2. A signaling system including'a long submarine signaling cable, means for transmitting marking and spacing impulses over said cable, modulating means connected to the receiving end of said cable to produce a high frequency current modulated in accordance with said impulses, and an adjustable resistance element and battery connected to said modulating means to 4compensate for the voltage `produced by said spacing impulses.

'V3.In a submarine cable communication system, -an emergency signaling system comprising calling apparatus for transmitting and responding solely to long calling impulses connected to said cable, a telegraph impulse transmitter, a shaping network connected thereto and connected to said cable., a telegraph signal receiving device connected to said cable and shaping network havinga modulator connected thereto, and a mechanical vibrator'connected to said modulato-r, and means for disconnecting said emergency signaling system from said submarine cable communicating system.

4. In an emergency signaling system for a submarine communication system comprising switching means for connecting said emergency Ysystem to said communication system, a telegraphV impulse transmitter connected to said switching means,V for transmitting marking and spacing impulses, a receiving circuit connected to said switching means for receiving marking and spacing impulses having an audible signal indicating device and a. mechanically driven modulator connectedV in said receiving system,

a mechanical loscillator mechanically connected to saidrmodulator, and a battery and variable resistance connected to said receiving circuit to compensate -for the voltage produced by the received spacing impulses, means for transmitting a call signal over said communication `system, and lmeans connected to said emergency signaling system for receiving and making audible said call signal. Y

AUSTEN M. CURTIS. 

